I have a commercially made alloy mast, possibly by Needlespar.
The heel fitting is similar to the type found on a standard rig, i.e. it sits inside the mast, with a tenon on the bottom. This tenon is then bolted to a slot in the step.
When I bought the boat the heel was not fixed in any way to the mast itself, (an attempt had been made to screw it in place but all the screws had sheared off).
There was a lot of movement at this point, and the mast being unstayed was presumably free to twist or even jump off the step. (The heel seems to extend only about an inch into the mast).
I have added some pop rivets through the mast but I am dubious as to the strength of this arrangement. Does anyone have any advice?